In vehicle technology for signal and data transmission, light conductors are becoming used in increasing numbers which, in contrast to a customary electrical signal conductors, provide substantial advantages. Among these advantages are their larger transmission bandwidths and their similarly small susceptibility in respect to electromagnetic disturbance fields. Optical signal couplings of the above mentioned kind are necessary if signals are to be transmitted not only within a vehicle but also between two vehicles coupled with one another, such as for example the cars of a vehicle train.
An optical signal coupling of the above mentioned kind is for example known from DE 28 54 962 C2, in which an intermediate buffer coupling for rail vehicles is described. A conductive coupling belongs to the intermediate buffer coupling which among other things serves to transmit impulses for the control of the braking and driving currents in a train of vehicles from one vehicle to the other. The conductive coupling consists of two contact carriers each of which is carried by a respective one of the wagons and in which along with a plurality of electrical contacts a light conductor is as well arranged. Of the two light conductors at least one is elastically biased so that the two light conductors are pressed against one another with their end faces when the contact carriers upon the coupling of the vehicles are moved against one another. Through these pressed together light conductors optical signals can be transmitted from one vehicle to the other.
In the case of such an optical signal coupling there however appear significant transmission failures. A reason for this lies in that the optical signals are heavily attenuated in their transmission from one light conductor to the other, both because of a dislocating movement as well as because of a tilting of the optical axes of the two light conductors relative to one another, which leads to a falsification of the optical signals. One such dislocating moment or such a tipping of the optical axes can however hardly be avoided in the case of vehicles which are coupled with one another, since the two coupling parts are not rigidly connected with one another and are relatively heavily mechanically stressed. Further reasons for an unreliable signal transmission lie in the sensitivity of such signal couplings to abrasion and contamination which, in view of the relatively rough conditions encountered in the use of vehicles, are likewise unavoidable.
To circumvent these problems an optical signal coupling is proposed in DE 29 22 937 C2 in which the light conductors are not pushed together at there end surfaces, and instead the light is transmitted with the help of lens pieces through the air from one light conductor to the other. Such a signal coupling is however relatively complicated and expensive and cannot offer the reliability which was expected of it.
In consideration of the above mentioned difficulties recently in DE100 52 020 A1 it has been proposed, in the case of applications under rough conditions, to do away entirely with a customary optical coupling of light conductors and instead of this to first convert the optical signals conducted in a first light conductor into electrical signals, to transmit these signals over customary electric couplings, to again convert the electrical signals into optical signals and to feed those optical signals into a second light conductor. With this solution, one loses above all the previously mentioned advantages of an optical signal coupling, namely the increased transmission bandwidth and a lower susceptibility to electromagnetic disturbing fields. Since however in the coupling regions of vehicles typically accompanying signals of high current are transmitted and thereby directly produce strong electromagnetic disturbing fields, it is not beneficial to replace the optical signal coupling by an electric coupling sensitive to the disturbing fields. Moreover, the coupling region of vehicles offers only a limited space for the signal coupling, so that optical signal couplings with their high transmission bandwidth are more efficiently used than electrical couplings.
The present invention has as its object the provision of an optical signal coupling which assures a reliable transmission of signals between vehicles coupled with one another.